Mean field theory and Monte Carlo simulation of phase transitions and magnetic properties of a tridimensional Fe₇S₈ compound

Abstract

The structural, electronic and magnetic properties of Fe 7 S 8 material have been studied within the framework of the ab-initio calculations, the mean field approximation (MFA) and Monte Carlo simulation (MCS). Our study shows that two forms of the iron atoms, Fe 2+ with spin S=2, and Fe 3+ with spin =5/2 are the most probable configurations. A mixed Ising model with ferromagnetic spin coupling between Fe 2+ and Fe 3+ ions and between Fe 3+ and Fe 3+ ions, and with antiferromagnetic spin coupling between Fe 2+ ions of adjacent layers has been used to study the magnetic properties of this compound. We demonstrated that the magnetic phase transition can be either of the first or of the second order, depending on the value of the exchange interaction and crystal field. The presence of vacancies in every second iron layer leads to incomplete cancellation of magnetic moments, hence to the emergence of the ferrimagnetism. Anomalies in the magnetization behavior have been found and compared with the experimental results.

Interatomic Interaction Models for Magnetic Materials: Recent Advances

“…Thus, instead of solving many-particle problem (11), we solve independent single-particle KS equations (14). These equations need to be solved self-consistently: we start from any randomly initialized density 𝑛(r), next we calculate the effective potential 𝑉 eff.…”

“…Nevertheless, this model continues to be widely used as a tool for investigating phase transitions through Monte Carlo simulations. [10,11] In less than a decade, a logical "extension" of the Ising formalism known as the classical Heisenberg model was proposed. This model, named after the ferromagnetic formalism proposed by Heisenberg, [6] lies between a full description of the electronic state and conventional micromagnetism.…”

“…Although the one-and two-dimensional Ising models have analytical solutions [8,9], the three-dimensional case remains unresolved. Nevertheless, this model continues to be widely used as a tool for investigating phase transitions through Monte Carlo simulations [10,11].…”

Nonequlibrium magnetic features in a mixed spin (2, 5/2) Ising system driven by the external oscillating magnetic field by path probability method

“…The system is a convenient prototypical model to investigate some molecular-based magnetic materials, such as AFe II Fe III [22], and AM II Fe III (C 2 O 4 ) 3 (A=N(n-C 3 H 7 ) 4 M=Mn, Fe) [17,23]. Very recently, the model was used to investigate the magnetic features of the Fe 7 S 8 compound by using by the mean-field theory and Monte Carlo Simulations [24]. The mixed spin (2, 5/2) IS was also utilized to investigate dielectric features of BiFeO3/YMnO3 bilayer films within the Monte Carlo Simulations [25].…”

Dynamic Magnetic Features of a Mixed‐Spin‐2 and Spin‐5/2 Ising Ferrimagnetic System under a Time‐Dependent Oscillating Magnetic Field: Path Probability Method Approach

“…De Le Espriella and co‐workers [ 25,26 ] investigated the magnetic behaviors of the model on a square lattice within the MCS. Moreover, the model utilized a study of thermal and magnetic features of the molecular‐based AFe II Fe III (C 2 O 4 ) 3 nanoribbons [ 27 ] and nanographene layer [ 28 ] within the MCS, the magnetic features of Fe 7 S 8 compound by using by the MFA and MCS, [ 29 ] and the dielectric features of BiFeO 3 /YMnO 3 bilayer films within the MCS, [ 30 ] and Fe 3 S 4 component within Ab‐initio calculations and the MCS. [ 31 ] The model also utilized a prototypical model to study some properties of nanomaterials, such as core/shell structure, [ 32 ] a bilayer nanoisland with a grapheme‐like structure, [ 33 ] a nanotube structure, [ 34 ] armchair graphene nanoribbons, [ 35 ] a monolayer coronene like nanostructure, [ 36 ] and nanographene.…”